This invention generally relates to a floating boat lift system for a watercraft which uses air to displace water in tanks to lift a watercraft (air-displacement floating boat lift).
The use of air displacement floating boat lifts are well known. A number of designs are currently known that provide this basic function. Most use a plurality of air tanks, connected to a blower and valves using hoses. Examples of these are U.S. Pat. Nos. 7,325,503, 5,860,379, Ser. No. 11/690,732, U.S. Pat. Nos. 6,547,485, 3,895,592, 4,018,179, 4,072,119. All of these designs use hoses to transfer the air from the blower to the air tank. The hoses often are routed underwater, exposed to UV light, and experience repetitive loading from wave action. All of these factors make the air hoses the most common cause for product failure for many of these designs.
A common problem with air displacement floating boat lifts is maintaining stability during lifting and launching. 5503 and 0732 address this by using stabilizing arms forming a four bar linkage. 2119 uses two pairs of trunnions. These arms can have durability issues since they experience high repetitive loading in a wavy environment. Designs similar to 5503 need to be attached to a U-shaped dock within limits of width, which can limit the locations for installation of this design. Designs without stabilizing arms, such as 0379 and 7485 often require the operator to adjust 4 air valves to maintain stability.
Designs like 5503 are comprised of bunks which support the boat, a frame which supports the bunks and secure the floats. Designs such as 0379 use air-filled bags to support the boat, which are not as durable, tend to have less lifting range, and are more difficult to secure in place. This design references an embodiment with level sensors and blow-out valves which would be used for leaks.
Another challenge for several designs such as 5503, 2097, 8179 and 0732 is connecting the frame to the plastic or fiberglass air tanks. High loading and fatigue loading can cause failures in plastic or fiberglass air tanks.
Fitting into a 10 ft slip has been a challenge for free-floating air displacement boat lifts since typical max boat beams are 8.5 ft (for highway regulations), which does not leave much space between the boat and dock. This invention is believed to be the first free-floating air displacement lift with rigid structure to fit in a 10 ft slip with an 8.5 ft boat